Interference Contributions Research Articles

Collectivity from interference

In hadronic collisions, interference between different production channels affects momentum distributions of multi-particle final states. As this QCD interference does not depend on the strong coupling constant αs, it is part of the no-interaction baseline that needs to be controlled prior to searching for other manifestations of collective dynamics, e.g., in the analysis of azimuthal anisostropy coefficients vn at the LHC. Here, we introduce a model that is based on the QCD theory of multi-parton interactions and that allows one to study interference effects in the production of m particles in hadronic collisions with N parton-parton interactions (“sources”). In an expansion in powers of 1/(Nc2 − 1) and to leading order in the number of sources N , we calculate interference effects in the m-particle spectra and we determine from them the second and fourth order cumulant momentum anisotropies vn{2} and vn{4}. Without invoking any azimuthal asymmetry and any density dependent non-linear dynamics in the incoming state, and without invoking any interaction in the final state, we find that QCD interference alone can give rise to values for vn{2} and vn{4}, n even, that persist unattenuated for increasing number of sources, that may increase with increasing multiplicity and that agree with measurements in proton-proton (pp) collisions in terms of the order of magnitude of the signal and the approximate shape of the transverse momentum dependence. We further find that the non-abelian features of QCD interference can give rise to odd harmonic anisotropies. These findings indicate that the no-interaction baseline including QCD interference effects can make a sizeable if not dominant contribution to the measured vn coefficients in pp collisions. Prospects for analyzing QCD interference contributions further and their possible relevance for proton-nucleus and nucleus-nucleus collisions are discussed shortly.

Direct CP Violation in K→μ^{+}μ^{-}.

A rare decay K_{L}→μ^{+}μ^{-} has been measured precisely, while a rare decay K_{S}→μ^{+}μ^{-} will be observed by an upgrade of the LHCb experiment. Although both processes are almost CP-conserving decays, we point out that an interference contribution between K_{L} and K_{S} in the kaon beam emerges from a genuine direct CP violation. It is found that the interference contribution can change K_{S}→μ^{+}μ^{-} standard-model predictions at O(60%). We also stress that an unknown sign of A(K_{L}→γγ) can be determined by a measurement of the interference, which can much reduce a theoretical uncertainty of B(K_{L}→μ^{+}μ^{-}). We also investigate the interference in a new physics model, where the ε_{K}^{'}/ε_{K} tension is explained by an additional Z-penguin contribution.

The contribution of pain in determining the health status of cancer patients with bone metastases: A secondary analysis of data from three Phase III registration trials

We aimed to provide a simple, descriptive health-status profile for cancer patients with bone metastases, based on the EuroQol EQ-5D, a tool commonly used to measure health utility scores, and to evaluate its association with the Brief Pain Inventory (BPI), a legacy pain-assessment tool. Although pain is one of five health-status dimensions measured by the EQ-5D, our understanding of how pain relates to the other EQ-5D dimensions is limited. We derived data from 5500 patients with bone metastases who completed the EQ-5D and BPI. Regression analyses examined how BPI severity and interference scores correlated with EQ-5D utility scores and how BPI items associated with EQ-5D items, for the entire sample and by disease-type subgroup. Regardless of cancer site, the percentage of patients reporting moderate/severe problems in each of the five EQ-5D dimensions were pain/discomfort, 78%; usual activities, 58%; mobility, 55%; anxiety/depression, 57%; and self-care, 26%. BPI pain interference explained more of the variability in the EQ-5D utility scores than did pain severity (R2 =41% vs. 34%). BPI worst pain, average pain, pain now, interference with general activity, and interference with work significantly predicted EQ-5D pain/discomfort, with odds ratio estimates <1. Pain/discomfort was the worst-rated dimension of the EQ-5D in this population, but the relationship of this item to BPI pain severity was modest, suggesting that the single pain item of the EQ-5D may be of limited utility in studies for which pain is an endpoint. Health-status dimensions include more than pain. We examine the contribution of pain severity and pain-related functional interference in determining the health status of cancer patients with bone metastases. The pain dimension from a health-status measure may be an inadequate metric in clinical trials/clinical practice when pain is an important outcome.

Intensity directed equalizer for the mitigation of DML chirp induced distortion in dispersion-unmanaged C-band PAM transmission

The directly modulated laser (DML) is one of the most cost-effective transmitter options in optical communication systems, but it introduces an additional impairment caused by the interaction between frequency chirp and chromatic dispersion for C-band transmission. In this paper, we propose a low-complexity intensity directed equalizer based on feedforward equalizer and decision feedback equalizer (FFE/DFE) to mitigate the chirp induced distortions, and remarkably improve the transmission performance of PAM signals generated by DML. The equalizer is based on the fact that the directly modulated PAM symbols with different intensity levels have different chirp frequencies, which will lead to different inter-symbol interference (ISI) contributions to their adjacent symbols due to the velocity difference caused by chromatic dispersion. To address this phenomenon, the proposed equalizer employs multiple sets of tap coefficients according to the intensity levels of PAM signals. With this equalizer and a commercial 16.8GHz DML, we demonstrate a 56Gb/s PAM4 transmission over a record 43km SSMF in the C-band without optical dispersion compensation under the 3.8 × 10−3 HD-FEC BER threshold.

A Restricted Open Configuration Interaction with Singles Method To Calculate Valence-to-Core Resonant X-ray Emission Spectra: A Case Study.

In this work, a new protocol for the calculation of valence-to-core resonant X-ray emission (VtC RXES) spectra is introduced. The approach is based on the previously developed restricted open configuration interaction with singles (ROCIS) method and its parametrized version, based on a ground-state Kohn–Sham determinant (DFT/ROCIS) method. The ROCIS approach has the following features: (1) In the first step approximation, many-particle eigenstates are calculated in which the total spin is retained as a good quantum number. (2) The ground state with total spin S and excited states with spin S′ = S, S ± 1, are obtained. (3) These states have a qualitatively correct multiplet structure. (4) Quasi-degenerate perturbation theory is used to treat the spin–orbit coupling operator variationally at the many-particle level. (5) Transition moments are obtained between the relativistic many-particle states. The method has shown great potential in the field of X-ray spectroscopy, in particular in the field of transition-metal L-edge, which cannot be described correctly with particle–hole theories. In this work, the method is extended to the calculation of resonant VtC RXES [alternatively referred to as 1s-VtC resonant inelastic X-ray scattering (RIXS)] spectra. The complete Kramers–Dirac–Heisenerg equation is taken into account. Thus, state interference effects are treated naturally within this protocol. As a first application of this protocol, a computational study on the previously reported VtC RXES plane on a molecular managanese(V) complex is performed. Starting from conventional X-ray absorption spectra (XAS), we present a systematic study that involves calculations and electronic structure analysis of both the XAS and non-resonant and resonant VtC XES spectra. The very good agreement between theory and experiment, observed in all cases, allows us to unravel the complicated intensity mechanism of these spectroscopic techniques as a synergic function of state polarization and interference effects. In general, intense features in the RIXS spectra originate from absorption and emission processes that involve nonorthogonal transition moments. We also present a graphical method to determine the sign of the interference contributions.

Spin-charge separation in an Aharonov-Bohm interferometer

We study manifestations of spin-charge separation (SCS) in transport through a tunnel-coupled interacting single-channel quantum ring. We focus on the high-temperature case (temperature $T$ larger than the level spacing $\Delta$) and discuss both the classical (flux-independent) and interference contributions to the tunneling conductance of the ring in the presence of magnetic flux. We demonstrate that the SCS effects, which arise solely from the electron-electron interaction, lead to the appearance of a peculiar fine structure of the electron spectrum in the ring. Specifically, each level splits into a series of sublevels, with their spacing governed by the interaction strength. In the high-$T$ limit, the envelope of the series contains of the order of $T/\Delta$ sublevels. At the same time, SCS suppresses the tunneling width of the sublevels by a factor of $\Delta/T$. As a consequence, the classical transmission through the ring remains unchanged compared to the noninteracting case: the suppression of tunneling is compensated by the increase of the number of tunneling channels. On the other hand, the flux-dependent contribution to the conductance depends on the interaction-induced dephasing rate which is known to be parametrically increased by SCS in an infinite system. We show, however, that SCS is not effective for dephasing in the limit of weak tunneling. Moreover, generically, in the almost closed ring, the dephasing rate does not depend on the interaction strength and is determined by the tunneling coupling to the leads. In certain special symmetric cases, dephasing is further suppressed. Similar to the spinless case, the high-$T$ conductance shows, as a function of magnetic flux, a sequence of interaction-induced sharp negative peaks on top of the classical contribution.

Transverse-momentum resummation for the signal-background interference in the H→γγ channel at the LHC

We present an upgraded calculation of the effects of resonance-continuum interference for the Higgs boson decaying to two photons at the Large Hadron Collider, at next-to-leading order in the strong coupling $\alpha_S$, $O(\alpha_S^3)$, and including transverse-momentum ($q_T$) resummation at next-to-leading logarithmic accuracy. We study the importance of the interference contribution in different transverse-momentum regions, with a particular focus on the low $q_T$ region $q_T^2 << Q^2$ (with $Q^2$ being the invariant diphoton mass) where resummation becomes essential for a reliable calculation.

Single Pion Production in Neutrino Reactions

An accurate model for single pion production should include single pion produced in resonant and non-resonant interactions as well as the interference contribution between them. The main effect of this correction can be visible in pion angular distributions that is represented in this work.

Deletion of Cytoplasmic Double-Stranded RNA Sensors Does Not Uncover Viral Small Interfering RNA Production in Human Cells.

Antiviral immunity in insects and plants is mediated by the RNA interference (RNAi) pathway in which viral long double-stranded RNA (dsRNA) is processed into small interfering RNAs (siRNAs) by Dicer enzymes. Although this pathway is evolutionarily conserved, its involvement in antiviral defense in mammals is the subject of debate. In vertebrates, recognition of viral RNA induces a sophisticated type I interferon (IFN)-based immune response, and it has been proposed that this response masks or inhibits antiviral RNAi. To test this hypothesis, we analyzed viral small RNA production in differentiated cells deficient in the cytoplasmic RNA sensors RIG-I and MDA5. We did not detect 22-nucleotide (nt) viral siRNAs upon infection with three different positive-sense RNA viruses. Our data suggest that the depletion of cytoplasmic RIG-I-like sensors is not sufficient to uncover viral siRNAs in differentiated cells. IMPORTANCE The contribution of the RNA interference (RNAi) pathway in antiviral immunity in vertebrates has been widely debated. It has been proposed that RNAi possesses antiviral activity in mammalian systems but that its antiviral effect is masked by the potent antiviral interferon response in differentiated mammalian cells. In this study, we show that inactivation of the interferon response is not sufficient to uncover antiviral activity of RNAi in human epithelial cells infected with three wild-type positive-sense RNA viruses.

Are One-Electron Bonds Any Different from Standard Two-Electron Covalent Bonds?

The nature of the chemical bond is perhaps the central subject in theoretical chemistry. Our understanding of the behavior of molecules developed amazingly in the last century, mostly with the rise of quantum mechanics (QM) and QM-based theories such as valence bond theory and molecular orbital theory. Such theories are very successful in describing molecular properties, but they are not able to explain the origin of the chemical bond. This problem was first analyzed in the 1960s by Ruedenberg, who showed that covalent bonds are the direct result of quantum interference between one-electron states. The generality of this result and its quantification were made possible through the recent development of the generalized product function energy partitioning (GPF-EP) method by our group, which allows the partitioning of the electronic density and energy into their interference and quasi-classical (noninterference) contributions. Furthermore, with GPF wave functions these effects can be analyzed separately for each bond of a molecule. This interference energy analysis has been applied to a large variety of molecules, including diatomics and polyatomics, molecules with single, double, and triple bonds, molecules with different degrees of polarity, linear or branched molecules, cyclic or acyclic molecules, conjugated molecules, and aromatics, in order to verify the role played by quantum interference. In all cases the conclusion is exactly the same: for each bond in each of the molecules considered, the main contribution to its stability comes from the interference term. Two-center one-electron (2c1e) bonds are the simplest kind of chemical bonds. Yet they are often viewed as odd or unconventional cases of bonding. Are they any different from conventional (2c2e) bonds? If so, what differences can we expect in the nature of (2c1e) bonds relative to electron-pair bonds? In this Account, we extend the GPF-EP method to describe bonds involving N electrons in M orbitals (N < M) and show its application to (2c1e) bonds. As examples we chose the molecules H2+, H3C·CH3+, B2H4-, [Cu·BH3(PH3)3], and an alkali-metal cation dimer, and we evaluated the components of the electronic energy and density, which account for the formation of the bond, and compared the results with those for the respective analogous molecules exhibiting the "conventional" two-electron bond. In all cases, it was verified that interference is the dominant effect for the one-electron bonds. The GPF-EP results clearly indicate that molecules exhibiting (2c1e) bonds should not be considered as special systems, since one- and two-electron bonds result from quantum interference and therefore there is no conceptual difference between them. Moreover, these results show that quantum interference provides a way to unify the chemical bond concept.

Interference effects in electron scattering from small water clusters

The importance of interference effects in electron scattering from complex molecular targets is demonstrated theoretically by an exemplificative case study of small water clusters. Interference contributions arising from all the scattering centres in the target lead to an increase of the elastic differential cross sections at small scattering angles and to the appearance of prominent minima in the cross sections of three-dimensional isomers which resemble structural properties of bulk water. The phenomena which are absent for isolated water molecules but emerge for small water clusters may help to better understand electron-driven processes in condensed aqueous media.

What is distressing about auditory verbal hallucinations? The contribution of goal interference and goal facilitation.

Distressing and pleasant/positive voices (auditory verbal hallucinations) are common in both clinical and non-clinical voice-hearers. Identifying factors that contribute to emotional reactions to voices is essential for developing effective psychological interventions. Several theories propose that facilitation and interference with personal goals are important predictors of distress and well-being. This study examined whether voice-related distress is related to the degree to which voices interfere with personal goals, and whether pleasantness of voices is influenced by the extent to which they facilitate goals. Cross-sectional with clinical and non-clinical voice-hearers. Twenty-two clinical and 18 non-clinical voice-hearers completed interviews and self-report measures assessing (1) personal goals, (2) content, characteristics, and affective reactions to voices, and (3) ratings of the extent to which voices facilitated and/or interfered with achievement of important personal goals. Affective reactions were strongly correlated with measures of goal interference and goal facilitation. Regression analyses revealed that these associations remained significant when controlling for important covariates (e.g., participant grouping; content, frequency and duration of voices). Goal interference was specifically associated with distress, whereas goal facilitation specifically predicted perceived pleasantness of voices. This study provides a novel perspective on the factors that might contribute to distress in people who hear voices. The findings suggest that perceived impact of voices on valued personal goals may be an important contributor of voice-related distress. We propose that clinical assessments, formulations, and interventions could benefit from the careful analysis of the perceived impact of voices on goals. These findings suggest that variability in voice-related distress is closely linked to the perceived impact of voices on personal goals. These strong effects observed highlight the importance of considering the role of personal goals in future research on the psychological mechanisms leading to distress associated with voice hearing. Psychological assessments may benefit from the careful exploration of the impact of voice hearing on valued goals, and interventions promoting control over personal goals may be explored as treatment options for clients with distressing voices.

Top-Bottom Interference Effects in Higgs Plus Jet Production at the LHC.

We compute next-to-leading order QCD corrections to the top-bottom interference contribution to H+j production at the LHC. To achieve this, we combine the recent computation of the two-loop amplitudes for gg→Hg and qg→Hq, performed in the approximation of a small b-quark mass, and the numerical calculation of the squared one-loop amplitudes for gg→Hgg and qg→Hqg, performed within OpenLoops. We find that QCD corrections to the interference are large and similar to the QCD corrections to the top-mediated Higgs production cross section. We also observe a significant reduction in the mass-renormalization scheme uncertainty once the next-to-leading order QCD prediction for the interference is employed.

Kinetics of atoms in a bichromatic field formed by elliptically polarised waves

The kinetics of atoms in a bichromatic field formed by waves with an arbitrary elliptical polarisation is considered. Analytical expressions are derived for the force and the friction and diffusion coefficients within the model of an atom with the jg = 1/2 → je = 3/2 optical transition. These expressions are presented in the general form as an expansion in gradients of light field parameters. Some specific features of the kinetics of atoms are found, which are due to the interference contributions to the friction and diffusion coefficients. The kinetics of atoms in the field of an optical lattice formed as a result of the interference of a wave with a uniform elliptical polarisation and a nonuniformly polarised dissipative field is analysed.

NNLO QCD counterterm contributions to [formula omitted] for the physical value of mc

One of the most important O(αs2) corrections to the B¯→Xsγ branching ratio originates from interference of contributions from the current–current and photonic dipole operators. Its value has been estimated using an interpolation in the charm quark mass between the known results at mc=0 and for mc≫12mb. An explicit calculation for the physical value of mc is necessary to remove the associated uncertainty. In the present work, we evaluate all the ultraviolet counterterm contributions that are relevant for this purpose.

Indirect exchange interaction between magnetic impurities near the helical edge

The indirect exchange interaction between magnetic impurities located in the bulk of a two-dimensional topological insulator decays exponentially with the distance. The indirect exchange interaction for magnetic impurities mediated by the helical states at the edge of the topological insulator demonstrates behaviour which is typical for the Ruderman-Kittel-Kasuya-Yosida interaction in a one-dimensional metal. We have shown that interference between the bulk and edge states in the two-dimensional topological insulator results in existence of the unusual contribution to the indirect exchange interaction which, on the one hand, decays exponentially with a distance at the length scale controlled by the Fermi energy of the edge states and, on the other hand, oscillates with distance along the helical edge with the period determined by the Fermi wave length. We found that this interference contribution to the indirect exchange interaction becomes dominant for such configurations of two magnetic impurities when one of them is situated close to the helical edge whereas the other one is located far away in the bulk.

Two-loop amplitudes for qg→Hq and qq¯→Hg mediated by a nearly massless quark

We compute the two-loop QCD corrections to $q g \to H q$ and $q \bar{q} \to H g$ amplitudes mediated by loops of nearly massless quarks. These amplitudes provide the last missing ingredient required to compute the NLO QCD corrections to the top-bottom interference contribution to the Higgs boson transverse momentum distribution at hadron colliders.

Improved analysis of the (O7,O7) contribution to B¯→Xsγγ at O(αs)

The present study is devoted for an improved analysis of the self-interference contribution of the electromagnetic dipole operator ${\mathcal{O}}_{7}$ to the double differential decay width $d\mathrm{\ensuremath{\Gamma}}/(d{s}_{1}d{s}_{2})$ for the inclusive $\overline{B}\ensuremath{\rightarrow}{X}_{s}\ensuremath{\gamma}\ensuremath{\gamma}$ process, where the kinematical variables ${s}_{1}$ and ${s}_{2}$ are defined as ${s}_{i}=({p}_{b}\ensuremath{-}{q}_{i}{)}^{2}/{m}_{b}^{2}$ with ${p}_{b}$, ${q}_{1}$, ${q}_{2}$ being the momenta of the $b$-quark and two photons. This calculation completes the next-to-leading-logarithmic (NLL) QCD prediction of the numerically important self-interference contribution of ${\mathcal{O}}_{7}$ by keeping the full dependence on the strange-quark mass ${m}_{s}$, which is introduced to control possible collinear configurations of one of the photons with the strange quark. Our results are given for exact ${m}_{s}$, in contrast to an earlier work where only logarithmic and constant terms in ${m}_{s}$ were retained. This improved NLL result for the $({\mathcal{O}}_{7},{\mathcal{O}}_{7})$-interference contribution shows that finite ${m}_{s}$ effects are only sizable near the kinematical endpoints of the spectrum $d\mathrm{\ensuremath{\Gamma}}/(d{s}_{1}d{s}_{2})$. At the level of the branching ratio, in the phase-space region considered in this paper, it is observed that $\text{Br}[\overline{\mathrm{B}}\ensuremath{\rightarrow}{\mathrm{X}}_{\mathrm{s}}\ensuremath{\gamma}\ensuremath{\gamma}]$ does not develop a sizable ${m}_{s}$ dependence: the impact on this branching ratio is less than 5% when ${m}_{s}$ is varied between 400--600 MeV. For the same phase-space region finite strange quark mass effects for the branching ratio are less than 7%.

Higgs production in association with off-shell top-antitop pairs at NLO EW and QCD at the LHC

We present NLO electroweak corrections to Higgs production in association with off-shell top-antitop quark pairs. The full process mathrm{pp}to {mathrm{e}}^{+}{nu}_{mathrm{e}}{mu}^{-}{overline{nu}}_{mu}mathrm{b}overline{mathrm{b}}mathrm{H} is considered, and hence all interference, off-shell, and non-resonant contributions are taken into account. The electroweak corrections turn out to be below one per cent for the integrated cross section but can exceed 10% in certain phase-space regions. In addition to its phenomenological relevance, the computation constitutes a major technical achievement as the full NLO virtual corrections involving up to 9-point functions have been computed exactly. The results of the full computation are supported by two calculations in the double-pole approximation. These also allow to infer the effect of off-shell contributions and emphasise their importance especially for the run II of the LHC. Finally, we present combined predictions featuring both NLO electroweak and QCD corrections in a common set-up that will help the experimental collaborations in their quest of precisely measuring the aforementioned process.

Episodic Memory and Age-Related Deficits in Inhibitory Effectiveness

Background/Study Context: Age-related deficits in inhibitory control are well established in some areas of cognition, but evidence remains inconclusive in episodic memory. Two studies examined the extent to which a loss in inhibitory effectiveness—as measured by the extent of retrieval-induced forgetting (RIF)—is only detectable in (1) the very old, and (2) that a failure to control for noninhibitory mechanisms can lead to the misinterpretation of intact inhibition in episodic memory in the very old.Methods: In Study 1, the authors employed a modified independent cue test—to provide as clean a measure of inhibitory functioning as possible—and examined whether there were significant differences in inhibitory effectiveness between younger-old (60–64 years), old (65–69 years), and older-old (70–74 years) adults. In Study 2, the authors directly manipulated the contribution of output interference (a noninhibitory mechanism) to RIF in a group of young adults (18–34 years), old (61–69 years), and older-old (70–85 years) adults.Results: In Study 1, both younger-old (60–64 years) and old (65–69 years) adults demonstrated RIF on the modified independent cue test but older-old (70–74 years) adults did not. In Study 2, all age groups demonstrated RIF in conditions where output interference was promoted. However, when output interference was controlled, only the young (18–34 years) and old (61–69 years) age groups demonstrated RIF; the older-old (70–85 years) age group did not.Conclusions: The findings suggest that inhibitory functioning remains intact in older adults under the age of 70 years. However, a misleading impression can be formed of inhibitory effectiveness in adults over the age of 70 when memory tests do not exclude the use of noninhibitory processes, such as output interference. These two issues may partly explain the previous inconclusive findings regarding inhibitory deficits in normal aging.